Hey 1QwkSport2.5r,

thank you for your answer,
yes i know, there is no much information for this engine with Tuned Pipe.
maybe some experience with the 91FX can help cause theoretically the calculation this semilar enouth (same exhaust port dimension - almost same angles for for open port and close port).
the Macs manual is familiar to me.. try to find kind of compare for my results

if anyone have more information, i will appreciate
thanks

Guy